In-Plane Seismic Frame Action Effects on Buckling-Restrained Brace Welded End Connection Performance

Abstract eng:
In-plane buckling-restrained brace (BRB) end rotation induced by frame action is a commonly observed phenomenon in buckling-restrained braced frames (BRBFs). However, its effect on BRB end connection performance has not yet been clear. In this study, the frame action of non-moment-resisting braced frame was summarized based on previously observed BRBF responses. Four BRB end deformation modes for quick determination of BRB end rotational demand are proposed considering different BRB arrangements, the story where BRBs locate, and the boundary condition of corner gussets connected with column base. Key factors affecting BRB end rotation and BRB end moment are examined theoretically by parametric analysis. Subassemblage tests of four BRB specimens under horizontal cyclic loading were conducted by adopting two loading frames to impose the expected frame action effects. It shows that the BRB end rotation subjected the BRB ends to significant flexural moments, leading to premature yielding of the BRB ends or end zone buckling. The frame action effects and the flexural rigidity of BRB ends were found to have significant influence on BRB end connection performance. The triggering moment induced by the BRB end rotation was the main contributor to BRB end moment. However, the moment amplification effect induced by the flexure of BRB end zones became prominent especially for small flexural rigidity of BRB ends.

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